Karl Johannes Max Strub (28 September 1900 – 23 March 1966) was a German violin virtuoso and eminent violin pedagogue. He gained a Europe-wide reputation during his 36 years of activity as primarius of the Strub Quartet. Stations as concertmaster led him from the 1920s to the operas of Stuttgart, Dresden and Berlin. Appointed Germany's youngest music professor at the Hochschule für Musik Franz Liszt, Weimar in 1926, he followed calls to the Berlin University of the Arts and, after the Second World War to the Hochschule für Musik Detmold. Strub was a connoisseur of the classical-romantic repertoire, but also devoted himself to modern music, among others he gave the world premiere of Hindemith's Violin Sonata No. 2 in D major. He promoted the music of Hans Pfitzner. Strub played on a Stradivari violin until 1945; numerous recordings from the 1930s/40s document his work.

Strub was born in 1900 as the eldest of three children of the photographer Otto Strub and his wife Ida, née Göhringer, in Mainz in the then Grand Duchy of Hesse-Darmstadt. His mother was the daughter of a cigarette manufacturer from the neighboring Biebrich, a district of Wiesbaden that was later incorporated. His sister Elisabeth married an American manufacturer with whom she was to settle in Weimar. Rosa, his younger sister, also spent most of her life there.

The father earned his living mainly with post-mortem photography. In his Mainz atelier in the Frauenlobstraße 25 in Neustadt, European violinists such as Willy Burmester, Joseph Joachim, Jan Kubelík and Henri Marteau as well as the still young Franz von Vecsey, whom he in turn photographed for free. Otto Strub was himself a passionate amateur violinist and supported Max musically to the best of his ability. There was a piano in his studio and he received his first piano lessons at the age of five. From the age of six he was taught violin by Alfred Stauffer, concertmaster of the Philharmonisches Staatsorchester Mainz. Kubelik recommended the ambitious father to contact the Viennese violin professor Otakar Ševčík. In his correspondence, however, he advised against a career as a musician for financial reasons.

In his native town, Strub attended the Rabanus-Maurus-Gymnasium, where he showed himself to be musically and artistically talented. He played in the school orchestra there, whose first violin he soon took over. The writer Carl Zuckmayer, four years his senior, with whom he was friends throughout his life, belonged to the cello group, Strub gave his first public concert at the age of twelve. He played with the Mainz orchestra Max Bruch's Violin Concerto No. 1 in G minor. Two years later, he performed Beethoven's Violin Concerto and the 3rd Piano Concerto in Frankfurt (then in Hessen-Nassau), among others. Zuckmayer retrospectively described the young Strub as a musical "child prodigy".

Strub, who was gifted for playing piano and violin, had to make a decision and – without Abitur – sixteen years old on the advice of the conductor Fritz Busch, brother of the violinist Adolf Busch, the decision to join the violin class of the former concertmaster of the Berlin Philharmonic at the Rheinische Musikschule [de]. Bram Eldering, a pupil of Joseph Joachim, to enter. Besides Strub, Adolf Busch and Wilhelm Stross were also trained by the Dutch music teacher Eldering. Together with his mother and younger sister, the underage student Strub lived with a landlord during the First World War. He was able to play until 1918 as second violinist at the orchestra rehearsals of the municipal Gürzenich Orchestra Cologne under the musical direction of Hermann Abendroth. He was open to all styles, including contemporary music. In 1918, Strub was awarded the Mendelssohn Prize in Berlin, combined with a performance under the conductor Otto Klemperer that was well-received in the local press. Together with the growing cello virtuoso Emanuel Feuermann he played Brahms' Double Concerto in A minor. He remained at the Cologne Conservatory for another year.

After a tour of Germany and Italy, in August 1921 the Landes music director Fritz Busch brought Strub to Stuttgart as concert master and thus successor to Karl Wendling at the orchestra of the Staatstheater Stuttgart. Strub, who had little orchestral experience at the time, was Busch's last choice after the application process had been disillusioned. Busch described him as a "first-rate violinist" and predicted a steep career for him. His contract obliged him to perform opera and symphony concerts, i.e. 10 performances plus rehearsals each, whereby he was released from rehearsals and from the operetta service. At the events in the opera, the concertmaster Reinhold Rohlfs-Zoll, who had been Wendling's representative for a time, was treated as an equal. Busch pursued a modern programming at the Landestheaterorchester, which was not always received positively by the critics. During Strub's period of service, in October 1921, Ewald Straesser's Fourth Symphony op. 44 premiered in the Stuttgart Kultur- und Kongresszentrum Liederhalle [de] . The private citizen Strub became acquainted with the Busch family of musicians and the conductor Busch later became godfather of his son Harald Strub, along with the violin teacher Eldering.

With Busch, who had been enticed away to Dresden, Strub moved to the Sächsische Staatskapelle Dresden of the Staatsoper Dresden (Semperoper) in 1922, where he took the position of first concertmaster. After his performance of Brahms' Violin concerto the orchestra decided unanimously for Strub. During his time with the orchestra in 1924 at the Staatsschauspiel Dresden, Busch was responsible for the premiere of Strauss’ Intermezzo, "bürgerlichen Komödie mit sinfonischen Zwischenspielen" (bourgeois comedy with symphonic interludes). In the same year, Strub was assigned the Dutch violinist Jan Dahmen as first concert master. After Strub had left the Saxon capital in favour of a career as a soloist and music teacher, he was succeeded by Karl Thomann.

In 1923, Strub replaced Gustav Havemann as first violinist in the Petri Quartet, to which the orchestra musicians Erdmann Warwas (2nd violin), Alfred Spitzner (alto) and Georg Wille (violoncello) belonged. According to the historian Michael Hans Kater, he soon surpassed his predecessor Havemann as a string player.